Ocs package

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Revision as of 23:09, 21 September 2015 by Cdf (talk | contribs) (A CMOS AND GATE)
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OCS : Octave Circuit Simulator

History and Motivation

Problem Formulation

Data Structure

File Formats

Tutorials

A CMOS AND GATE

Schematic for a CMOS AND gate

Here we show how to set up the simulation of the CMOS AND gate in the figure. The circuit has

  • 9 Elements
    • 6 MOSFETs (3 n-type + 3 p-type)
    • 3 Voltage sources

Below we show three methods for constructing the circuit data structure

Once the circuit data structure is loaded the simulation can be started by the following commands

Code: Run the AND gate simulation
x         = [.5 .5 .33 .66 .5 1 0 0 1 ]';
t         = linspace (0, .5, 100);
pltvars   = {"Va", "Vb", "Va_and_b"};
dmp       = .2;
tol       = 1e-15;
maxit     = 100;
out       = tst_backward_euler (outstruct, x, t, tol, maxit, pltvars);

Click on the figure to the right to see the simulation results

Result of the CMOS AND gate switching simulation

Build the AND GATE structure directly

Build the AND gate circuit structure parsing an IFF netlist

Code: Load the AND circuit structure parsing an IFF netlist
outstruct = prs_iff ("and");
Code: IFF netlist for the AND gate (.cir file)
% 0.1b1
% A Simple CMOS AND GATE
%
% N-Mosfets
% There are 3 N-Mosfets
Mnmosfet simple 4 3
3 3
k          Vth		rd
1e-4       0.1		1e7
1e-4       0.1		1e7
1e-4       0.1		1e7
1 3 4 0 
2 0 3 0 
4 0 5 0 
%
% P-Mosfets
Mpmosfet simple 4 3
3 3
k           Vth		rd
-1e-4       -0.1	1e7
-1e-4       -0.1	1e7
-1e-4       -0.1	1e7
1 6 4 6 
2 6 4 6 
4 6 5 6
%
% Input voltage sources
Mvoltagesources sinwave 2 4
2 4
Ampl      f       delay     shift
0.5       1       0.0       0.5
0.5       2       0.25      0.5
1 0  
2 0  
END
%
% Power supply
Mvoltagesources DC  2 1
1 1
V
1
6 0  
END
Code: IFF netlist for the AND gate (.nms file)
% 0.1b1
1 Va
2 Vb
5 Va_and_b
6 Vdd
7 I1
8 I2 
9 I3
Code: Model evaluator file for simple MOSFET models
function [a,b,c] = Mnmosfet (string, parameters, parameternames, extvar, intvar, t)   
  
  switch string

    case 'simple',
      
      rd = 1e6;
      
      for ii=1:length(parameternames)
        eval([parameternames{ii} "=",...
              num2str(parameters(ii)) " ;"])    
      endfor
      
      vg   = extvar(1);
      vs   = extvar(2);
      vd   = extvar(3);
      vb   = extvar(4);
      
      vgs  = vg-vs;
      vds  = vd-vs;
      
      if (vgs < Vth)
        
        
        gm = 0;
        gd = 1/rd;
        id = vds*gd;
        
      elseif ((vgs-Vth)>=(vds))&(vds>=0)
        
        id = k*((vgs-Vth)*vds-(vds^2)/2)+vds/rd;
        gm = k*vds;
        gd = k*(vgs-Vth-vds)+1/rd;
        
      elseif ((vgs-Vth)>=(vds))&(vds<0)
        
        gm = 0;
        gd = 1/rd;
        id = vds*gd;
        
      else # (i.e. if 0 <= vgs-vth <= vds)
        
        id = k*(vgs-Vth)^2/2+vds/rd;
        gm = k*(vgs-Vth);
        gd = 1/rd;
        
      endif
      
      a = zeros(4);
      
      b = [ 0     0         0   0;
           -gm   (gm+gd)   -gd  0; 
            gm  -(gm+gd)    gd  0;
            0     0         0   0];
      
      c = [0 -id id 0]';
      break;

    otherwise

      error(["Mnmosfet: unknown option " string]);
      
  endswitch

endfunction


Build the AND gate circuit structure parsing a .spc file

Code: Load the AND circuit structure parsing a .spc file
outstruct = prs_spice ("and");


Code: Load the AND circuit structure parsing a .spc file
outstruct = prs_spice ("and");